The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
An aircraft is provided in general with a propulsion assembly comprising a turbojet engine surrounded by a nacelle. The turbojet engine generally includes, upstream, fan blades actuated by an engine. The fan blades are surrounded by a casing allowing mounting said turbojet engine in the nacelle.
The fan of the turbojet engine is composed essentially of a rotating shaft carrying a plurality of vanes. At their radial end, the vanes are surrounded circumferentially by a casing. The fan casings are generally machined metallic elements.
The turbojet engine can be a bypass turbojet engine capable of generating a hot air flow (also called primary flow) coming from the combustion chamber of the turbojet engine, and a cold air flow (secondary flow) coming from the fan and which circulates outside the turbojet engine through an annular channel, also called “flow path”, formed between a fairing of the turbojet engine and an inner wall of the nacelle. At the rear of the nacelle, both the primary and secondary flows mix together.
This nacelle is generally equipped with a thrust reverser.
During landing of an aircraft, the thrust reverser allows improving the braking ability of the aircraft by redirecting forward at least a part of the thrust generated by the turbojet engine. In this phase, the thrust reverser obstructs the gas ejection nozzle and directs the ejection flow of the engine to the front of the nacelle, thereby generating a counter-thrust which adds to the braking of the wheels of the aircraft.
More specifically, a nacelle generally exhibits a structure comprising an air inlet upstream of the engine, a median structure intended to surround the casing of the turbojet engine, and a downstream structure comprising an Inner Fixed Structure (“IFS”) and an Outer Fixed Structure (“OFS”) intended to surround the combustion chamber of the turbojet engine and accommodating the thrust reversal means.
The thrust reversal means are diverse and can be in the form of at least a movable cowl, called “thrust reverser cowls”, moving in translation thanks to actuators along a direction substantially parallel to a longitudinal axis of the nacelle.
During this phase of flight, the structure of the thrust reverser is subjected to axial aerodynamic forces which tend to push back longitudinally the thrust reversal means relative to the turbojet engine.
In order to support the movable thrust reverser cowls and connect the downstream section to the median section via the fan casing, the downstream section comprises fixed elements and, in particular, longitudinal beams connected upstream to an outer fixed structure comprising a substantially annular assembly called front frame, formed in one or more portion(s) between said longitudinal beams, and intended to be fixed to the periphery of the downstream edge of the fan casing of the engine.
The structure of the thrust reverser is generally made of two half portions articulated into an upper portion on the pylon, called “D-duct” or “C-duct” structure.
In this configuration, the holding between the fan casing and the front frame is achieved by a male portion, generally carried by the front frame, cooperating in a female portion, generally carried by the casing.
More particularly, the front frame is connected to the fan casing by fixation means generally of the knife-edge/throat type comprising a substantially annular flange, made from one or several portion(s), secured to the front frame and cooperating with a J-shaped or V-shaped groove, commonly referred to as J-ring.
Such a holding assembly is not adapted for nacelles in which the rear portion is capable of sliding during maintenance operations (nacelle called or O-duct) towards the rear of the nacelle along a substantially longitudinal direction of the latter.
Indeed, in such a configuration of the nacelle, it would be appropriate to anticipate one or several segment(s) of the downstream section opening laterally so as to be able to space apart the flange from the throats and free the front frame from the casing.
Several systems of connection between the downstream section and the fan casing compatible with a nacelle of the O-duct type, thenceforth, have been developed.
There is known in particular the setting up of an assembly for holding the interface of the outer fixed structure of a nacelle of the turbojet engine casing, comprising:                a first protruding element belonging to the upstream end of the outer fixed structure;        a second protruding element belonging to the downstream end of the casing;        
said at least first and second protruding elements being configured for coming into contact with one another;                two half-rings formed by a wall defining a housing, configured to receive the first and second protruding elements when the casing and the outer fixed structure are mounted edge-to-edge, and abutting means configured to hold the first and second protruding elements in the housing.        
This holding assembly thus allows connecting, by a connecting flange formed of two half-rings, the downstream end of the casing and the upstream end of the outer fixed structure of the downstream structure accommodating the thrust reversal means.
In a conventional manner, the two half-rings can be fixed together by fixation means, which provides the tightening and holding force of the protruding elements.
In a known manner, the fixation means can include locking elements such as a three-point hook lock, one of the half-rings supporting the portion of the lock that includes the hook and the other half-ring supporting the portion that comprises the retaining member of said hook.
Moreover, locking elements comprise an actuating handle pivotally mounted on one of the ends of the connecting flange and a connecting rod interposed between the other end of the flange and a portion of the handle separate from the axis of rotation of this handle.
Such a device allows pre-stressing the connecting flange when it is in the closed position.
However, with the known locking elements, the opening of the half-rings of the connecting flange depends on the circumference dimensions specific of the nacelles on which the locking element and the flange are installed.
Thus, the locking elements must be adapted specifically to nacelles with particular circumference dimensions.
This multiplies the references of parts and the production costs, in order to be adapted to each one of the manufactured nacelles.
A posed problem is, thereafter, to provide a fixed position of the connecting flange when it is in the open position, for a same stroke of the handle regardless of the variations of the circumference dimensions of the concerned nacelle.